the eye movements change. it takes a little bit of time before the structure of the brain starts to change from the stroke. that's actually the winl doe of opportunity to intervene. so it takes hours for the mri, actually a couple days for the mri to really show up the stroke some of the time. we've seen false negatives out to two days. >> my understanding, am i wrong, that if you can get to the hospital within the first three hours of a stroke you can ameliorate some of the difficulties that come from it? >> that's correct. so clot-busting drugs have been used to about 4 1/2 hours after a stroke. and this is an opportunity for us to intervene in patients with new early strokes. we've put these on people as early as an hour or two after the start. >> okay. may look rinky-dink but it also looks painless. >> painless and easy. >> no needles. >> thank you, doctor. >>> an important part of our home at "cbs this morning," a map of the world. but it's no ordinary map, don't you know. the man who made it famous was a